Hello, I have tried running a code given to me to predict a pseudo out-of-sample forecast using a loop of autoregression, but I only get syntax error. I suspect I must download an extension or something, but I'm not sure. I would appreciate any help!
Here's my code:

local start = tq(2003q1)
local end = tq(2012q4)

gen forecast = .

forvalues i = `start'/`end' {

* AR(2) regression ;
reg d_infl L(1/2).d_infl if quarter >= tq(1963q1) & quarter <=`i', robust

* forecast for the next period ;
replace forecast = _b[_cons] + _b[L1.d_infl]*L1.d_infl+ _b[L2.d_infl]*L2.d_infl if quarter == `i' + 1 ;
}